Field of Invention
The present invention relates to a liquid crystal display (LCD), and more particularly, the present invention relates to a wide viewing angle LCD utilizing light diffraction to improve its viewable range.
Description of Related Art
With rapid advancement of the fabrication technology of thin film transistors, and because of the advantages the liquid crystal display (LCD) device, such as lightness, thinness, low power consumption, and no harmful radiations, the LCD device has been widely applied on various electronic products such as television, personal digital assistant, notebook, digital camera, video camera, recorder, and mobile phone, etc. However, since not being a self-luminous display, the LCD device generally needs a backlight source to generate light which is then guided to pass through optical films such as diffusion layers and brightness enhancement films (BEF), thereby forming a uniform planar light emitted into an LCD panel for showing images. A twisted nematic (TN) or super twisted nematic (STN) LCD device is one of the popular LCD devices. Although the TN or STN LCD device may have an advantage of competitive price, yet the viewing angle of such display is smaller than that of a wide viewing angle LCD (for example, a multiple-domain vertical alignment (MVA) display, an in-plane switching (IPS) display, or a fringe field switching (FFS) display, etc.).
The so-called viewing angle means an angle within a range that an observer can observe the image shown by a display with a certain quality. For example, for a desktop LCD, a user often looks at the desktop LCD in a normal viewing angle. Thus, due to different alignments of liquid crystal molecules lead to different optical effects, a designer will take the image quality of the display corresponding to the normal viewing angle as a main consideration when designing the displays. When looking at the display in an oblique viewing angle, an observer may perceive a difference (such as brightness difference or chroma difference) between an image observed in the normal viewing angle and the image observed in the oblique viewing angle, and the difference becomes greater with increase of a observing angle of the observer. Among common LCDs, the TN LCD has the most serious viewing angle problem described above.
In comparison to the TN LCD having the problem of poor viewing angle, a vertical alignment (VA) LCD provides another option for the people to meet their demands of wide viewing angle.
Although the VA LCD may have a wider viewing angle than the TN LCD, yet the VA LCD still has some disadvantages, such as unsymmetrical viewing angles, so that those in this industry often adopt a multi-domain vertical alignment (MVA) technology to overcome the disadvantages. Besides, another problem for the VA LCD is the color shift problem, i.e. the color differences between a main viewing angle and other viewing angle are quite large. Those in this industry mostly use more complicated pixel designs collaborated with signal designs to improve the aforementioned problem.
Although these designs may improve the viewing angle of the VA LCD, yet these designs may also result in the problems of lowered process yield, lowered aperture ratio, increased total cost, etc. in accompany with the complicated pixel or signal designs.
Therefore, there is a need to provide a display device for simultaneously improving the image quality about brightness and chroma, including contrast, gray level inversion, deviation of gamma curve, and color shift issues, etc.